Model airplanes built for flight including radio controlled model airplanes are typically equipped with small gas engines to propel the aircraft. These engines are typically started by hand, that is using the fingers to spin the propeller and the connected engine crankshaft until the model airplane engine catches and runs independently. A typical way of accomplishing this is by holding the model aircraft in one hand and then using the free hand to spin the propeller, thereby mechanically operating the engine until the engine catches. A serious limitation of this method of starting the model plane engine is that the person starting the plane may have fingers, hand, face, forearm and possibly hair and clothing near or in potential contact with the aircraft propeller. When the task succeeds and the engine eventually comes to life, the spinning propeller can inflict serious injury to the person starting the engine. Typical model airplane engines operate in the vicinity of 10,000 to 25,000 revolutions per minute, and so the risk of bodily injury to a person having parts of the body in or near the path of a spinning propeller is quite substantial. Larger gas model engines make the task of hand starting even more difficult due to the increased torque required to crank the engine, together with the higher torques achieved by the larger engines in operation and therefore increased risk of bodily injury from a spinning propeller when starting the engine.
In starting a model aircraft engine it is advantageous to spin the engine at higher revolutions per minute (RPMs) than can be readily achieved by hand cranking the engine. Spinning the engine at higher RPMs can provide a hotter spark to the spark plug or glow plug while at the same time more quickly clearing a possible flooded condition, which is quite difficult to clear by hand cranking alone.
Hand-held electrically powered starter motors designed for use in starting model airplane engines are commonly available from a number of manufacturers. Typically electric starters are powered from a convenient and portable 12V DC power source such as a car battery or the smaller lawn tractor or motor cycle battery. Such starters are often equipped with a rubber boot on the end of the starter drive shaft. The rubber boot is designed to press against the cone cap of the propeller and thereby transmitting the rotary torque of the starter to the plane propeller and gas engine. This rubber boot method of coupling the starter to the model engine is workable, however, it may require an undesirable amount of force to be applied to the airplane propeller cone cap and model to achieve sufficient frictional coupling to transmit enough torque to spin the model airplane engine for starting. Not all model airplanes are equipped with propeller cone caps, some have a bolted on propeller and in such cases the rubber drive boot on the electric starter may not be sufficient to crank and start the model engine.
Therefore, a device which is designed to interface a variety of model airplane starters to a model airplane, which improves the mechanical torque transfer coupling between the starter and the airplane propeller and engine allowing sufficient starting torque to be delivered to the gas engine from the starter, a device that overcomes the slippage and limited torque transmission capabilities of the prior art starter coupling methods, that further reduces the need for hand starting and improves operator safety by removing hands, fingers, clothing from the vicinity of the model aircraft engine during starting, such a device for use in starting a model airplane engine would be useful and novel.